Department of NanoBiophotonics, Research Group Mitochondrial Structure and Dynamics, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany; Clinic of Neurology, High Resolution Microscopy of the Cell, University Medical Center Göttingen, 37075 Göttingen, Germany.
Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.
Cell Rep. 2021 Nov 23;37(8):110000. doi: 10.1016/j.celrep.2021.110000.
In human cells, generally a single mitochondrial DNA (mtDNA) is compacted into a nucleoprotein complex denoted the nucleoid. Each cell contains hundreds of nucleoids, which tend to cluster into small groups. It is unknown whether all nucleoids are equally involved in mtDNA replication and transcription or whether distinct nucleoid subpopulations exist. Here, we use multi-color STED super-resolution microscopy to determine the activity of individual nucleoids in primary human cells. We demonstrate that only a minority of all nucleoids are active. Active nucleoids are physically larger and tend to be involved in both replication and transcription. Inactivity correlates with a high ratio of the mitochondrial transcription factor A (TFAM) to the mtDNA of the individual nucleoid, suggesting that TFAM-induced nucleoid compaction regulates nucleoid replication and transcription activity in vivo. We propose that the stable population of highly compacted inactive nucleoids represents a storage pool of mtDNAs with a lower mutational load.
在人类细胞中，通常将单个线粒体 DNA（mtDNA）压缩成称为核区的核蛋白复合物。每个细胞包含数百个核区，这些核区往往会聚集成群。目前尚不清楚所有核区是否都同等参与 mtDNA 复制和转录，或者是否存在不同的核区亚群。在这里，我们使用多色 STED 超分辨率显微镜来确定原代人细胞中单个核区的活性。我们证明只有少数核区是活跃的。活性核区在物理上更大，并且往往同时参与复制和转录。不活跃与线粒体转录因子 A（TFAM）与个体核区 mtDNA 的高比例相关，这表明 TFAM 诱导的核区紧缩调节体内核区复制和转录活性。我们提出，高度紧缩的非活性核区的稳定群体代表了具有较低突变负荷的 mtDNA 的存储池。
